This invention relates to a trocar for puncturing the body wall to provide access to a surgical site during endoscopic surgery. More specifically, it relates to a trocar having an obturator which incorporates a puncturing tip, and the unique attachment of the tip to the supporting stem of the obturator.
The surgical trocar has become the mainstay in the development and acceptance of endoscopic surgical procedures. Endoscopic surgery involves the performance of surgery through a number of openings having a relatively small diameter. These openings are made with the trocar, which typically includes a trocar obturator and a trocar cannula. The obturator is the piercing implement which punctures the body wall to make the opening. The obturator slidingly fits into the trocar cannula, which is essentially an access tube. The obturator is initially fitted into and through the cannula so that the piercing tip of the obturator extends from the distal end of the cannula. Pressure is exerted on the body wall with the piercing tip, and the puncture is made through the body wall. Once the puncture is made, the obturator is withdrawn from the cannula. The cannula then provides a small diameter passageway into and through the body wall to provide access for additional surgical instrumentation to the desired surgical site.
One of the significant advances in the development of the trocar is described in U.S. Pat. No. 4,535,773. This patent describes the use of a spring-loaded safety shield interposed between the obturator and inner wall of the trocar cannula. In its unbiased position, the shield covers the puncturing tip of the obturator. When pressure is applied against the body wall, the shield retracts to expose the blade. When the body wall is punctured, the pressure is relieved and the safety shield springs back to cover the puncturing tip. In this way, inadvertent puncture of internal organs is substantially lessened.
The puncturing tip of the trocar obturator has conventionally been configured in the shape of a cone or a pyramid. More recently, it has been found that a flat, razor blade can provide less trauma to tissue during puncture. See, for example, U.S. Pat. No. 5,314,417. Regardless what tip geometry is used, it is necessary during the manufacture of the trocar obturator to attach the puncturing tip to the remaining components of the obturator. In essence, the obturator consists of three primary components. These components are the obturator handle, stem and puncturing tip. The handle is the component which the user grips when puncturing the body wall. At the opposite end of the obturator handle is the puncturing tip. Supporting the puncturing tip and providing the connection between the tip and the obturator handle is the stem. The stem is typically a long, rigid rod. The connection between the stem and the puncturing tip is critical for safe and efficient performance of the trocar. This may be especially true depending on the particular geometrical configuration of the puncturing tip.
The puncturing tip of an obturator conventionally includes a collar or thread for fastening the tip to the stem of the obturator. Alternatively, the tip may simply incorporate a notch, and the stem may be press fit into the notch. Although these attachment techniques may be adequate under normal conditions, they may be inadequate when high loads or rotational torque is present at the puncturing tip as the body wall is being punctured. Additionally, when the puncturing tip is a flat razor blade as described in the '417 patent, the connection between the blade and the stem may not provide the optimum transition from the blade to the stem to reduce trauma to the tissue as the trocar is inserted into the tissue.
Accordingly, an improved trocar is needed within the surgical community. In particular, this trocar would have an obturator which incorporates an improved attachment between the puncturing tip of the obturator and its stem. This attachment ideally would be easy to assemble and provide a puncturing tip which is secure and resists pull-off and torque during high loads. Further, such an ideal attachment would not require additional obturator parts, and would also enable the user to disconnect the stem from the puncturing tip if desired. Finally, when a safety-shielded trocar with a flat, razor blade obturator tip is used, the connection between the tip and the stem of the obturator would provide a smoother transition from the tip to the stem, and ultimately to the safety shield, so that trauma to tissue as the tissue is punctured is substantially reduced.